1. Field of the Invention
The present invention relates to a body fat measuring apparatus, in particular, a body fat measuring apparatus capable of measuring visceral fat with high accuracy.
2. Description of the Background Art
As a method for measuring visceral fat, in recent years, there has been known a method for capturing an abdominal cross-sectional image using an X-ray CT, an MRI and the like and determining an area of a fat region occupying the cross-sectional image. Further, as another method, there has been disclosed a method which places a pair of electric-current electrodes on a back portion and an umbilical portion of an abdominal portion, places a pair of detection voltage electrodes on both flank portions, determines a bioelectrical impedance of the abdominal portion from the detected voltage between the voltage electrodes during energization between the electric-current electrodes and determines visceral fat from the bioelectrical impedance (refer to, for example, Japanese Patent Laying-Open Nos. 2001-252257 and 2002-369806, and a literature “Development of Visceral-Fat Measuring Method by Abdominal Bioelectrical Impedance Method”, Study of Obesity, Vol. 9, No. 2, 2003). Further, as a bioelectrical-fat measuring method using a bioelectrical impedance analysis, there has been disclosed a method which places electric-current electrodes on four limbs, energizes between the electric-current electrodes, places a pair of voltage electrodes at arbitrary two points between the electric-current electrodes provided on the four limbs and determines the impedance between the arbitrary two points (refer to, for example, U.S. Pat. No. 5,335,667).
Out of the aforementioned visceral-fat measuring methods, the method using an abdominal cross-sectional image taken through an X-ray CT or an MRI has a problem that it involves a large-size apparatus and therefore measurements of visceral fat can be performed only in medical institutions equipped with such facilities and can not be readily conducted everywhere.
Further the visceral fat measuring methods disclosed in the aforementioned two publications and the aforementioned literature are predicated on the fact that visceral fat exists as a lump at the center of the abdominal portion, as a measurement principle. However, visceral fat is stuck on the mesenterium in an actual human body and is distributed to some degrees, rather than exists as a lump. Therefore, these methods have the problem of inaccuracy of measurements.
Furthermore, although visceral fat can be measured through two-point measurements at parts with simple-shaped tissue like four limbs as described in the USP, the impedance of the abdominal portion is affected by the distribution of subcutaneous fat and internal fat, which makes it impossible to accurately measure visceral fat only thorough two-point measurement.